Using an imaging technique that can show axonal damage in the brain,
a group of Canadian researchers have found a connection between axonal
damage and the common MS symptom fatigue. They analyzed proton magnetic
resonance spectroscopy images from 73 people with MS, and found that the
N-acetylaspartate-creatine ratio (NAA/Cr), an indicator of axonal damage,
was significantly higher in subjects reporting high levels of fatigue than
those less affected by fatigue. The association with this ratio was independent
of a number of other factors measured, including disability (EDSS), lesion
volume, age, and disease duration.

It is still not known exactly how axonal damage would produce fatigue
symptoms, but the authors speculate that the need to recruit other areas
of the brain to compensate for damaged regions may be responsible. The
usefulness of this study and others like it will hopefully extend to therapy
development, as it may now be easier to predict which drugs would or would
not have an effect on MS-related fatigue given the mechanisms involved.